The patch titled
Subject: selftests: vm: add hugetlb_shared userfaultfd test to run_vmtests.sh
has been added to the -mm mm-unstable branch. Its filename is
selftests-vm-add-hugetlb_shared-userfaultfd-test-to-run_vmtestssh.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-vm-add-hugetlb_shared-userfaultfd-test-to-run_vmtestssh.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Subject: selftests: vm: add hugetlb_shared userfaultfd test to run_vmtests.sh
Date: Mon, 8 Aug 2022 10:56:10 -0700
Patch series "userfaultfd: add /dev/userfaultfd for fine grained access
control", v5.
Why not ...?
============
- Why not /proc/[pid]/userfaultfd? Two main points (additional discussion [1]):
- /proc/[pid]/* files are all owned by the user/group of the process, and
they don't really support chmod/chown. So, without extending procfs it
doesn't solve the problem this series is trying to solve.
- The main argument *for* this was to support creating UFFDs for remote
processes. But, that use case clearly calls for CAP_SYS_PTRACE, so to
support this we could just use the UFFD syscall as-is.
- Why not use a syscall? Access to syscalls is generally controlled by
capabilities. We don't have a capability which is used for userfaultfd access
without also granting more / other permissions as well, and adding a new
capability was rejected [2].
- It's possible a LSM could be used to control access instead, but I have
some concerns. I don't think this approach would be as easy to use,
particularly if we were to try to solve this with something heavyweight
like SELinux. Maybe we could pursue adding a new LSM specifically for
this user case, but it may be too narrow of a case to justify that.
[1]: https://patchwork.kernel.org/project/linux-mm/cover/20220719195628.3415852-1-axelrasmussen@xxxxxxxxxx/
[2]: https://lore.kernel.org/lkml/686276b9-4530-2045-6bd8-170e5943abe4@xxxxxxxxxxxxxxxx/T/
This patch (of 5):
This not being included was just a simple oversight. There are certain
features (like minor fault support) which are only enabled on shared
mappings, so without including hugetlb_shared we actually lose a
significant amount of test coverage.
Link: https://lkml.kernel.org/r/20220808175614.3885028-1-axelrasmussen@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20220808175614.3885028-2-axelrasmussen@xxxxxxxxxx
Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Reviewed-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
Cc: Gleb Fotengauer-Malinovskiy <glebfm@xxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Nadav Amit <namit@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Zhang Yi <yi.zhang@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/vm/run_vmtests.sh | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/tools/testing/selftests/vm/run_vmtests.sh~selftests-vm-add-hugetlb_shared-userfaultfd-test-to-run_vmtestssh
+++ a/tools/testing/selftests/vm/run_vmtests.sh
@@ -121,9 +121,11 @@ run_test ./gup_test -a
run_test ./gup_test -ct -F 0x1 0 19 0x1000
run_test ./userfaultfd anon 20 16
-# Test requires source and destination huge pages. Size of source
-# (half_ufd_size_MB) is passed as argument to test.
+# Hugetlb tests require source and destination huge pages. Pass in half the
+# size ($half_ufd_size_MB), which is used for *each*.
run_test ./userfaultfd hugetlb "$half_ufd_size_MB" 32
+run_test ./userfaultfd hugetlb_shared "$half_ufd_size_MB" 32 "$mnt"/uffd-test
+rm -f "$mnt"/uffd-test
run_test ./userfaultfd shmem 20 16
#cleanup
_
Patches currently in -mm which might be from axelrasmussen@xxxxxxxxxx are
selftests-vm-add-hugetlb_shared-userfaultfd-test-to-run_vmtestssh.patch
userfaultfd-add-dev-userfaultfd-for-fine-grained-access-control.patch
userfaultfd-selftests-modify-selftest-to-use-dev-userfaultfd.patch
userfaultfd-update-documentation-to-describe-dev-userfaultfd.patch
selftests-vm-add-dev-userfaultfd-test-cases-to-run_vmtestssh.patch
